Method of establishing a shielded container wall opening

ABSTRACT

A method of establishing a shielded container wall opening including providing a metal container wall panel having an adhesively bonded protective layer selected from the group consisting of polyolefin copolymers of polyolefin-ethylene and ionomers of polyolefin. Providing a score line defined removable sector within the metal panel and an operating pull tab secured thereto. Thermally treating the container wall having the integral opening device at about 275* to 375*F for about 0.2 second to 4 minutes and preferably about 300 to 350*F for about 0.5 to 3 minutes. Operating the pull tab to initate fracture of the score line and establish an opening in the container wall. Simultaneously elongating portions of the protective layer disposed in a generally underlying position with respect to the score line and severing the same to provide a shielding edge which is disposed protectively against the opening defining wall of the metal container wall panel. Feathering preferably including an average projection of about .002 to .010 inch beyond the metal opening defining wall.

United States Patent [111 3,800,395 Gayner et al. 1 Apr. 2, 1974 [54]METHOD OF ESTABLISHING A SHIELDED 3,610,462 10 1971 Saunders 220 906 xCONTAINER WALL OPENING [75] Inventors: Herbert Gayner, Monroeville;David primary Exammer (,:,harlic Moon A. Smith, Penn Hills both of Pa.Attorney, Agent, or lirmArnold B. S|lverman [73] Assignee: A luminumCompany of America, [57] ABSTRACT Pittsburgh, Pa.

A method of establishing a shielded container wall l22l F'led: Sept15,1972 opening including providing a metal container wall 2 Appi 2 3panel having an adhesively bonded protective layer selected from thegroup consisting of polyolcfin co- Related Apphcatlon Data polymers ofpolyolefin-ethylene and ionomers of poly- [62] Division of Ser, No.190,479, Oct. 19, 1971, Pat. No. olefin. Providing a score line definedremovable sector 3,735,393 within the metal panel and an operating pulltab secured thereto. Thermally treating the container wall LS. havingthe integral pening device at about 275 to 1 Int. Cl. 375F for aboutecond to 4 minutes and prefera- [58] Field of Search 29/426, 427, 413;bly about 300 to 350 fo about 0,5 to 3 i 5 113/12] R, 121 220/53, 54Operating the pull tab to initate fracture of the score line andestablish an opening in the container wall. Sil l References Citedmultaneously elongating portions of the protective UNITED STATES PATENTSlayer disposed in a generally underlying position with 2,209,209 7/1940Ruby 29/426 respect to the Score and severing the Same 9 3,342,3679/1967 Drland... 220/54 vide a Shielding g which is disposed Proteclwely3,445,027 5/1969 Palmer... 220/54 against the opening defining wall ofthe metal con- 3,447,713 6/1969 Stec, 220/54 tainer wall panel.Feathering preferably including an 3,519,022 /1 0 H r 229/54 averageprojection of about .002 to .010 inch beyond 3,527,377 9/1970 Colby cta1 1220/54 h meta] opening d fi i 3,612,340 10/1971 Heffran 220/54 X3,632,461 1/1972 Gayner 220/53 6 Claims, 5 Drawing Figures WENTEDAPR2.914 3800.395

' sum 1 or 2 FIG. 2.

PATENFEDAPR 21m 3800 395 sum 2 [1F 2 This is a division of applicationSer. No. 190,479, filed Oct. 19, 1971, now Pat. No. 3,735,893.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention isdirected toward a method of establishing a shielded opening definingcontainer wall automatically with the operation of an integral openingdevice to establish a container wall opening. More specifically, thisinvention relates to such a method wherein a protective layer iselongated and severed to provide a feathered shielded projection aroundthe container wall opening. 1

2. Description of the Prior Art The advantages of providing a containerwall such as a can end or closure, for example, with integral openingdevices which permit the consumer to gain access to the containercontents without the need for a separate opening instrument have beenknown. One of the more popular conventional devices of this type employsa metal container wall having a scored or weakened line defining aremovable sector which is adapted to be either completely separated fromthe remainder of the container wall or partially separated in order toprovide an opening therein. It has been known to make advantageous useof a lever pull tab secured within the removable sector. Operation ofthe lever pull tab provides a mechanical advantage in initiatingfracture of the scored or weakened line and in providing for subsequentcontinued severance of the line.

One ofthe difficulties which has been encountered in connection withsuch opening devices is that complete or partial removal of the scoreline defined sector results in the remaining portion of the containerwall having an irregular, rather sharp opening defining wall whichrepresents a hazard to the consumer. Not only is there a risk that theconsumer will inadvertently suffer injury through direct contact withthe exposed ragged edge but also there is the additional disadvantagethat theproduct might be damaged during removal from the container as aresult of such contact.

A number of means of attempting to provide shielding structures whichresist such undesired results have been known. US. Pat. No. 3,303,962provides a preformed inwardly projecting radial bead in the containerbody which is adapted to' reduce the likelihood of undesired contactwith the raw edge on the container wall. In addition to preformingportions of the container wall in an effort to obtain shielding, it hasalso been known to provide independent shielding elements which areadapted to serve the same function. U.S. Pats. Nos.

3,447,713 and 3,527,377 provide preformed annular elements which arepositioned underlying the periphery of the end wall in such a positionas to be closely adjacent to the ragged metal edge and provide shieldingafter opening of the container has been effected. It has also been knownto provide shielding of the tear strip element edges, as opposed to thecontainer opening edges, by means of separate preformed, separateoversized web of material secured to the undersurface of the tear strip.US. Pat. No. 3,442,416 provides such a structure wherein a preformedrectangular web which is oversized with respect to the tear strip,remains attached to the tear strip upon opening and projects beyond thetear strip edges.

There remains, therefore, a need for a method of establishing a shieldedcontainer opening which method does not involvethe use of independentpreformed shielding elements and results in creation of the desiredshielding structure during opening of the container wall.

SUMMARY OF THE INVENTION The above-described need has been met by themethod of this invention. The method of this invention involvesproviding a metal container wall panel having an adhesively bondedprotective layer selected from the group consisting of polyolefins,copolymers of polyolefins and ethylene and ionomers of polyolefin. Ascore line defined removable sector is provided within t he met al paneland an operating pull tab is secured thereto, preferably by means of anintegrally formed rivet. After establishmentof the integral openingdevice and prior to operation of the same, the composite container wallis subjected tothermal treatment at about 275 to 375F for about 0.2second to 4 minutes and preferably at about 300 to 350F for about 0.5 to3 minutes. 1

In operating the structure of the present invention, the pull tab isemployed to initiate fracture of the score line in the metal panel.Simultaneously with such severance, the underlying protective layer issubjected to thinning elongation in regions generally underlying thescore line and is severed in order to establish a projection whichextends generally upwardly and inwardly so as to shield the raw edge ofthe remaining portion of the container wall after the removable sectorhas been withdrawn. The projection, which is preferably feathered, willdefine an opening of smaller dimension than will the metal panel openingdefining wall. The feathered projection preferably extends beyond themeta] opening defining wall by an average of about 0.002 to 0.010 inch.

It is an object of this invention to provide an integral opening devicecontainer wall adapted to establish shielding of the container wall rawedge simultaneously with the establishment of the opening throughoperation of the opening device.

It is another object of this invention to provide such a constructionwherein such shielding is effected through elongation and severance of aprotective layer underlying and adhesively secured to the metal panel.

It is an additional object of this invention to provide such a methodwhich is adapted to be readily employed in connection with conventionalcontainer wall manufacturing equipment and container sealing equipment,as well as preserving conventional consumer practices in opening suchcontainers.

These and other objects of this invention will be more fully understoodand appreciated from the following detailed description of the inventionon reference to the illustrations appended hereto.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates a plan view of oneform of container wall contemplated by this invention;

FIG. 2 is an elevational cross sectional illustration, partially brokenaway, taken through 2-2 of FIG. 1;

FIG. 3 is a cross sectional illustration of a portion of a containerassembly of this invention shown after score line severance has beeninitiated;

FIG. 4 is an elevational cross sectional illustration of a modified formof construction of this invention showing a different form of protectivelayer;

FIG. 5 is a fragmentary illustration of the container wall of FIG. 4taken after severance of the removable sector.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As used herein the termcontainer wall" shall refer to a portion of a container which isprovided with an integral opening device and serves as a structural partof the container and shall include can ends and jar and bottle closuresas well as container portions falling within this description.

Referring now to FIGS. 1 and 2, there is shown a container wall in theform of a can end. The container wall has a top panel 2 and a flangeportion 4 which terminates in a generally downwardly directed flangeextension 6. The can end has a removable sector 8 defined within the toppanel 2 by means of score line 10. As used herein, the term removablesector shall refer to container wall portions which are adapted to bepartially or totally severed in order to establish an opening throughwhich access may be had to the contents of the container. Forconvenience of reference, the term score line" shall refer to varioustypes of weakened lines which are so provided as to define a removablesector and yet maintain some residual metal within the score lineregions. Score line shall be used to refer to lines created byindentation tools as well as other panel weakening means and thesingular shall be deemed to refer to either the singular or plural. Asis shown in FIG. 1, a lever pull tab 14 is secured within the removablesector 8 by means ofa rivet 16, which may conveniently be establishedwithin the panel 2 as an integrally formed rivet.

In effecting opening of the container wall, the lifting portion 18 ofthe pull tab 14 is raised upwardly so as to cause the attaching end 20to initiate severance of score line 10. After score line severance hasbeen initiated in this fashion, the lever tab 14 may beemployed tocontinue severance of the score line until such time as the removablesector 8 is completely detached from the remainder of top panel 2.

Referring now to FIG. 2, there is shown a can end of the type shown inFIG. 1, with the pull tab 14 and attaching rivet 16 not shown. The metalpanel portion 24 of the composite container wall shown in FIG. 2 may becomposed of any material having the desired properties. Aluminum, steel,and alloys of the same are particularly suited for use with such ends.The term aluminum as used herein shall refer to any grade of aluminumand aluminum base alloys wherein aluminum consists of not less than 80percent by weight of the total composition.

A protective layer 26 is secured, preferably continuously, to the metalpanel 24 by means of adhesive layer 28. The protective layer 26 isselected from the group consisting of polyolefin, copolymers ofpolyolefm and ethylene and ionomers of polyolefin. Among thespecifically preferred materials are polypropylene and a copolymer ofpolypropylene and ethylene. With respect to the latter material, apreferred range of ethylene constituent is about 2 to I0 percent, byweight, with about 2 to 5 percent by weight being the preferred ethylenecontent. The protective layer 26 preferably may have a thickness ofabout 1 to 4 mils, with about 2.5 to 3.5 mils being preferred. Theprotective layer 26 preferably is provided in the form ofa film in orderto facilitate handling and joinder, but a coating may be employed shouldthis be desired.

The adhesive 28 preferably is selected from the group consisting ofepoxy, polyester and polyurethane. It will be appreciated that variousadditives which have a modifying influence on the properties of theseadhesivcs may be employed. For example, an epoxy modifled polyurethanehas proved to be an effective adhesive material. In addition,conventional catalysts and other additive materials may be employed withthe adhesives. The adhesives are preferably provided as a coating inamounts of about 1.0 to 5.0 milligrams per square inch with about 1.0 to3.0 milligrams per square inch being the preferred weight.

It has been found that such composite container walls have exceptionalcorrosion resistant properties, as well as resistance to destructionduring forming of integral opening devices in such container walls.

Referring now to FIG. 3, there is shown a cross sectional representationof a container wall 32 of this invention. The container wall has beensecured to a can body 34 by means of an interlocking seam. Protectivelayer 46 is secured to the panel 38 by means of adhesive 48. In theposition shown, the pull tab 36, which is secured to panel 38 by meansof rivet 40, has been employed to initiate severance of the score line42 in the portion shown toward the right of this figure. It will benoted that the panel 38 in the region of severance has an inwardlyprojecting sharp edge 44 defining the opening in panel 38. In initiatingfracture of the score line, portions of the protective layer 46 havebeen stretched, thinned and subsequently severed to establish featherededges 50, 52. Edge 52 projects generally radially inwardly and upwardlyand provides a shield against sharp edge 44 of panel 38 within theopening defining regions thereof. The term feathering as used hereinshall refer to the extent to which an edge 52 extends radially inwardlybeyond sharp edge 44. While for convenience of illustration the edges50, 52 have been shown as extending upwardly and inwardly, it will beappreciated that the shielding action may be provided by an edge 52which extends substantially completely inwardly with little or no upwardextension or by a projection which extends substantially completely inan upwardly direction with only little inward extension. In thoseinstances where the amount of stretching and thinning prior to fractureof protective layer 46 is slight the amount of taper in the feathered"edge may be less than that illustrated in FIGS. 3 and 5.

In the preferred practice of this invention, a feathered edge 52 whichhas such a projection of about 0.002 to 0.010 inch will be established.This establishes a restricted opening in protective layer 26 which is ofsmaller dimension than the opening defined by the sharp edge 44 of panel38. Referring now to FIG. 5, there is shown, somewhat schematically, across section of an end having a pour type opening wherein there is seenthat the panel edges 44 define an opening T, while the feathered edges52 define an opening R which is less than T. It is noted that thefeathered edge 52 will preferably provide a shield against sharp edge 44substantially continuously around the opening in panel 38 in order toeffect a complete shield.

Referring to H0. 4, there is shown a modified form of the inventionwherein a composite container wall 60 has a pull tab 62 secured theretoby means of an integrally formed rivet 64. A removable sector 68 isdefined by score line 70 and is of the pour type variety. in this formof the invention, rather than providing a protective layer which issubstantially coextensive with the container wall 60, as was the case inconnection with the forms shown in the previous drawings, the protectivelayer 74 completely covers only the removable sector 68 and the regionimmediately beyond the removable sector. The protective layer 74 issecured to the undersurface of the container wall 60 bymeans of adhesive76. This embodiment of the invention functions automatically toestablish a shield during container opening in the same fashion as thatdescribed above.

it has been found that the method of this invention not only producesthe desired feathered effect for shielding purposes, but also separationof portions of the protective layer from the container wall due torelease of the adhesive bonds securing the same to the panel (hereinreferred to as diaphragming) is also eliminated. Substantiallycontinuous bonding between the protective layer and removable sector notonly eliminates diaphragming but also provides automatic thinning andseverance of the protective layer portion when the removable sector issevered.

In preparation of the container wall of this invention, the containerwall is thermally treated after establishment of the integral openingdevice in order to establish the desired strength character-isticsin theprotective layer. it is preferred that the composite container wall beheated to about 275 to 375F for about 0.2 second to 4 minutes with thepreferred form involving heating of the container wall to a temperatureof about 300 to 350F for about 0.5 to 3 minutes. As a result of thisthermal treatment, diaphragming is effectively eliminated and severanceof the removable sector results in thinning of the protective layer andestablishment of a feathered shielding projection having an av- I erageradial-inward extension of about 0.002 to 0.010 inch. I

EXAMPLE movable sector and securing a lever pull tab therewithin bymeans of an integral rivet. The end was heated at 325F for 2 minutes.Upon opening of the end by severing of the score line, the underlyingprotective polypropylene-ethylene copolymer layer was fracturedgenerally in the region underlying the score line after having beenelongated. This established the feathered .edge which provided a shield.The feathered edge projected an average of about 0.004 inch into theopening defined by the metal panel.

It will, therefore, be appreciated that the method of this inventionpermits the use of conventional equipment in establishing a containerwall structure which will automatically establish a shield by severanceof a protective layer composed of a specifically selected material.Rather than requiring the manufacture and securement of a separatepreformed annular shield, the present invention provides for automaticestablishment of a feathered shield during normal opening of thec0ntainer wall in a conventional fashion. in addition, this results incustom tailoring the shield proportions and structural configuration inaccordance with the dimensions and configurations of the removablesector without the need to provide separate shields having varyingshapes corresponding to the removable sector. Also, there need be noconcern with variations in tolerance with respect to size and positionof the removable sector within the metal panel.

Various modifications may be made in the invention without departingfrom the spirit thereof or the scope of the claims, and therefore, theexact form shown is to be taken as illustrative only and not in alimiting sense and it is desired that only such limitations shall beplaced thereon as are imposed by the prior art or are specifically setforth in the appended claims.

We claim:

1. A method of establishing a shielded container wall opening comprisingproviding a metal container wall panel having an adhesively bondedprotective layer selected from the group consisting of polyolefins;copolymers of polyolefin and ethylene, and ionomers of polyolefin, a taboperated score line defined opening device in the metal panel and saidcontainer wall having been thermally treated at about 275 to 375F forabout 0.2 second to 4 minutes after'establishment of the said integralopening device, operating said lever pull tab to sever and at leastpartially remove said removable sector, and simultaneously with saidseverance of said removable sector severing said protective layer afterestablishing elongation thereof in regions generally underlying saidscore line so as to provide a feathered portion thereof projectingbeyond and shielding the opening defining portion of said container wallpanel.

2. The method of claim 1 including elongating said protective layerprior to fracture thereof to establish an average inward featheredprojection of greater than about'0.002 inch upon protective layerseverance.

3. The method of claim 2 including maintaining a substantiallycontinuous intimate adhesive bond be tween said removable sector andsaid underlying protective layer during severance of said removablesector.

4. The method of claim 2 including said protective layer is selectedfrom the group consisting of polypropylene and polypropyleneethylenecopolymers having an ethylene content of about 2 to 10 percent byweight, and

establishing said protective layer opening with an opening size of about2 to 7 percent less than said metal panel opening.

5. The method of claim 3 including providing said adhesive from thegroup consisting of epoxy, polyester and polyurethane,

thermally treating said container wall assembly at about 300 to 350F forabout 0.5 to 3 minutes subsequent to establishment of said integralopening device, but prior to securement of said container wall panel toa filled container.

3,800,395 7 8 6. The method of claim including 4 mils, and providingsaid protective layer from the group consisting of polypropylene andcopolymers of polyp py and ethylene wherein the ethylene Com definingprotective layer which has an average pro tent is about 2 to 5 percentby wgight, 5 jection of about 0.002 to 0.0l0 mils. said protective layerhaving a thickness of about 1 to establishing a feathered projection onsaid opening UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIONPatent No, 3,800,395 Dated pril 2, 1.974

lnventofls) Herbert Gayner et a1 It is certified that error appears inthe above-identified patent and that said Letters Patent are herebycorrected as shown below:

In the Abstract, line 4 After "polyolefin" f insert Col. 1, line 64After "of" delete "separate" and insert -a-'.

Signed and sealed this 24th day of September 1974.

(SEAL) Attest:

MCCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner ofPatents FORM PO-1050 (10-69) uscoMM-Dc 60376-P69 a US. GOVERNMENTPRINTING OFFICE: I969 0-366-334.

1. A method of establishing a shielded container wall opening comprisingproviding a metal container wall panel having an adhesively bondedprotective layer selected from the group consisting of polyolefins,copolymers of polyolefin and ethylene, and ionomers of polyolefin, a taboperated score line defined opening device in the metal panel and saidcontainer wall having been thermally treated at about 275* to 375*F forabout 0.2 second to 4 minutes after establishment of the said integralopening device, operating said lever pull tab to sever and at leastpartially remove said removable sector, and simultaneously with saidseverance of said removable sector severing said protective layer afterestablishing elongation thereof in regions generally underlying saidscore line so as to provide a feathered portion thereof projectingbeyond and shielding the opening defining portion of said container wallpanel.
 2. The method of claim 1 including elongating said protectivelayer prior to fracture thereof to establish an average inward featheredprojection of greater than about 0.002 inch upon protective layerseverance.
 3. The method of claim 2 including maintaining asubstantially continuous intimate adhesive bond between said removablesector and said underlying protective layer during severance of saidremovable sector.
 4. The method of claim 2 including said protectivelayer is selected from the group consisting of polypropylene andpolypropylene-ethylene copolymers having an ethylene content of about 2to 10 percent by weight, and establishing said protective layer openingwith an opening size of about 2 to 7 percent less than said metal panelopening.
 5. The method of claim 3 including providing said adhesive fromthe group consisting of epoxy, polyester and polyurethane, thermallytreating said container wall assembly at about 300* to 350*F for about0.5 to 3 minutes subsequent to establishment of said integral openingdevice, but prior to securement of said container wall panel to a filledcontainer.
 6. The method of claim 5 including providing said protectivelayer from the group consisting of polypropylene and copolymers ofpolypropylene and ethylene wherein the ethylene content is about 2 to 5percent by weight, said protective layer having a thickness of about 1to 4 mils, and establishing a feathered projection on said openingdefining protective layer which has an average projection of about 0.002to 0.010 mils.